The present invention relates to an air-conditioner, an outdoor unit and a refrigeration unit using vapor compression refrigeration cycle, and in particularly, is preferable to those which enable a motor installed in a compressor to be driven by commercially available power source and, by which a wide range from low cost products till high cost products and commonness are progressed and kind expansion is facilitated.
As refrigerant compressors used in air conditioners, outdoor units and refrigeration units using vapor compression refrigeration cycle, a constant speed type compressor which is driven at a substantially constant speed, an inverter type compressor whose rotational speed is controlled have been used, and induction motors incorporating cage type conductors (windings) are often employed since they can be easily driven by an A.C. voltage of a commercial frequency and so forth. Further, it has been known that D.C. motors are often employed having a rotor formed by providing permanent magnets to a rotor core and a rotor formed by providing three-phase windings to a rotor core from a view point of high efficiency, as disclosed in JP-A5-211796.
Further, as motors for industry, an embedded magnet synchronous motor which can be driven by a commercially available electric power has been proposed, in view of the need of energy saving, and it is disclosed in xe2x80x9cThe Super Economotor and its Applicationsxe2x80x9d by Hirano et al, in Yasukawa Technical Bulletin Vol. 62 NO. 4, 1998, Series Volume No. 241.
In the above-mentioned prior art, the motor disclosed in JP-A-5-211796 is advantageous in view of its high efficiency, but in order to start the motor, it is indispensable to use an inverter, as a power source, whose frequency is variable. A power source circuit or the like becomes complicated, and in the case of a system having a refrigeration cycle, it becomes excessively complicated in a certain application, so as to be expensive.
Further, in order to use the embedded magnet synchronous motor of the above-mentioned prior art, in an air conditioner, an outdoor unit and a refrigeration unit in which refrigeration cycle is used, consideration should be taken to the discharge volume of refrigerant necessary for the refrigeration cycle and the efficiency of the refrigeration cycle also with respect to the rotational speed of the motor, for example, and further, it must avoid that the volume of a compression chamber of the compressor, the size of the overall compressor and the size of the outdoor unit in which the compressor is installed become large.
Further, upon starting the refrigeration cycle, if the differential pressure between the suction side and the discharge side of the compressor is large, there is a possibility that the start becomes impossible even when the embedded magnet synchronous motor is used or its reliability becomes insufficient.
Further, if overload occurs during steady-state operation of the refrigeration cycle, that is, operation in synchronized condition, a rotor in the embedded magnet synchronous motor greatly stalls, or the temperature of the windings of the motor increases. In the worst case, the material of the windings would be deteriorated or the insulation of the windings would be broken, so that the reliability of the device would remarkably be deteriorated.
In addition, it is required to minimize the affection of the permanent magnets in the embedded magnet synchronous motor to deterioration of the refrigerant and lubrication oil circulating through the refrigeration cycle.
An object of the present invention is to provide an air conditioner, an outdoor unit and a refrigeration unit, using a refrigeration cycle which can reduce power consumption, which is highly efficient, which can be driven by commercially available power source and which is highly reliable.
An another object of the present invention is to decrease the volume of a compression chamber in a compressor, the size of the overall compressor, and sizes an outdoor unit in which the compressor is installed and the refrigeration unit (including an air-conditioner) even though their efficiency is high.
It is noted that the present invention is to achieve at least one of the above-mentioned subject matters and objects.
To achieve the above subject matters, according to the present invention, there is provided an air-conditioner comprising a refrigeration cycle including a compressor driven by a motor, an outdoor heat-exchanger and an indoor heat-exchanger, the motor being located in a motor chamber within a closed-container, and refrigerant gas passing through the motor chamber, the motor including cage conductors and permanent magnets which are magnetized in bipolar condition so that the motor serves as a synchronous motor, provided on a core in a rotor and the motor is driven by a commercially available power source.
With this arrangement, the refrigeration cycle is operated by the commercially available motor, and accordingly, the air-conditioner can be simplified as a system having a refrigeration cycle, and can be used for various applications in a wide range. Further, the permanent magnets embedded in the rotor are magnetized in bipolar state, and therefore, steady-state operation of the refrigeration cycle can be performed at a relatively high speed (3000 r/min, 3600 r/min) even though the commercially available power source has a low frequency of 50 or 60 Hz. Further, the compressor, the outdoor unit, the refrigeration unit and the like can be small-sized and compact, and these become advantages in enhancement of efficiency of the refrigeration cycle and in reduction of noise. In particular, the efficiency of the refrigeration cycle can be further enhanced in view of the following facts in combination: the motor becomes synchronous during steady-state operation and power against slip becomes unnecessary, no variation in the speed of the compressor occurs even though a load is increased due to variation in the outside air temperature, so that the compression efficiency does not lower, and the refrigeration cycle itself can be stable even though load variation occurs to the refrigeration cycle.
Further, a compression mechanism part can be commonly used with variable speed type air-conditioners and the like in which an inverter is used, and expansion of kinds is easily and inexpensive can be achieved.
Further, upon starting, the refrigerant liquid is returned into the compressor by a large quantity to lower the viscosity of lubrication oil, and upon starting for heating operation, the rise-up of the air-conditioner deteriorates. However, because the refrigerant gas is led through the motor chamber and the motor is driven in an asynchronous condition until it is synchronized after it is started by a commercially available power source, heat generated by the motor heats the refrigerant and the lubrication oil, so that it is possible to prevent bearings in the compressor from being damaged to enhance the heating capability.
Further, according to the present invention, there is provided an air-conditioner comprising a refrigeration cycle including a compressor driven by a motor, an outdoor heat exchanger and an indoor heat-exchanger, the motor for driving the compressor in combination of an induction motor and a synchronous motor, the induction motor comprising conductors adapted to heat refrigerant or lubrication oil in the refrigeration cycle, wherein during heating operation, the motor is operated as the induction motor to start the refrigeration cycle, and thereafter the motor is operated as the synchronous motor.
With this arrangement, at least during heating operation, the refrigeration cycle is started by the motor used as the induction motor, and therefore, heat generated by the motor heats the refrigerant and the lubrication oil to prevent the lowering of viscosity thereof, and accordingly, it is possible to prevent bearings in the compressor from being damaged, and to enhance the heating capacity. Nevertheless, thereafter the motor is turned into a synchronized condition in which the speed of the compressor is not changed, so that it is possible to prevent the compression efficiency from lowering even though the load becomes larger due to variation in the temperature of the outside air.
Further, in the above-described air conditioner, it is preferable to provide a circuit bypassing the discharge side and the suction side of the compressor and a shut-off valve for opening and closing this circuit to stard the refrigeration cycle after the shut-off valve is opened.
Further, in the above-described air conditioner, it is preferable to provide a circuit bypassing the discharge side and the suction side of the compressor, a shut-off valve for opening and closing the circuit and a discharge pressure detecting device to open the shut-off valve when a value detected by the discharge pressure detecting device exceeds a set pressure value during operation of the refrigeration cycle.
Further, in the above-described air conditioner, it is desirable to provide a liquid receiver located between the outdoor heat-exchanger and the indoor heat-exchanger, a refrigerant introducing and delivering pipe for introducing the refrigerant into the liquid receiver, a bypass pipe bypassing gas refrigerant in the liquid receiver into the downstream side in view of the flowing direction of the refrigerant, and a shut-off valve incorporated in the bypass pipe to open the shut-off valve when the discharge pressure of the compressor exceeds a set pressure value during operation of refrigeration cycle.
Further, in the above-described air conditioner, it is desirable to use a scroll compressor as the above-mentioned compressor since the inertial force of an orbiting scroll member and the like which are rotary components is small to facilitate the starting thereof and the refrigeration cycle itself can be stabilized even though the load exerted upon the refrigeration cycle varies and noise is reduced.
Further, in the above-described air conditioner, it is desirable to coat outer surfaces of the permanent magnets in view of preventing the refrigerant and the lubrication oil from deteriorating.
Further, according to the present invention, there is provided an air-conditioner comprising a refrigeration cycle including a plurality of compressors driven by a motor an outdoor heat-exchanger and an indoor heat-exchanger, the plurality of compressors comprising a capacity control type variable speed compressor and a constant speed compressor driven by the motor in which cage type conductors and permanent magnets magnetized in bipolar state are provided to a core of a rotor, and a check valve provided on a discharge side of the constant speed compressor.
With this arrangement, even during the variable speed compressor being operated, it is possible to easily start the constant speed compressor by a commercially available electric power by reducing differential pressure between the discharge side pressure and the suction side pressure of the constant speed compressor, and even when the capacity is increased greatly, the range of capacity variation can be increased without correspondingly increasing the inverter power source, and further, fine control can be made.
Further, according to the present invention, there is provided an outdoor unit comprising a compressor driven by a motor and an outdoor heat-exchanger, the motor being accommodated in a motor chamber in a closed container, wherein the compressor comprises a scroll compressor and the motor comprises cage type conductors and permanent magnets magnetized in bipolar state, which are provided in a core of a rotor.
Further, according to the present invention, there is provided a refrigeration unit comprising a compressor driven by a motor,, a condenser, a liquid receiver, an expansion valve and an evaporator, the motor being accommodated in a motor chamber in a closed container, wherein the compressor comprises a scroll compressor having a fixed scroll and an orbiting scroll, and the orbiting scroll is driven by the motor in which cage type conductors and permanent magnets are embedded in the core of the rotor.